Use larger MK's of rockets in thier rocket launchers, or use groups of them. I've found that calvalry troops in mass say groups of 5 can devastate tanks as they are generally smaller targets and also are usually more manueverable

DARN
Heavy Destroyer Class Carrier Hybrid HODGEPODGE
# odds and ends: a motley assortment of things
# patchwork: a theory or argument made up of miscellaneous or incongruous ideas

I've always ruled that you can pack up to a Mk. III rocket into a bazooka if you can find one.

However, as infantry you're going to want to focus on disabling a tank rather than destroying it. You don't have the firepower to punch through the armor, but you might be able to snap a tread or jam the turret.

I have spider mines, portable lasers, emp devices and various MK rockets. For MK1 missiles I have rocket-sticks (represented by harpoon pieces). I have ruled these can be fired from most weapons that physically allow it (e.g. an autopistol, represented by a western gun, cannot fit a harpoon piece).

I just made some shoulder-cannons for something I'm working on. I'm thinking that they'll have an infinite supply of either MKII or MKIII rockets that they can fire using my rules, which means that they don't need actual rockets, but it takes a turn to "reload."

Set up a "trap" of sorts, if you will: a stand offering "free" beer to anyone who can provide a valid tank piloting license--the catch being that the beer is only free if said pilot downs an entire six pack within the space of one turn. Consuming that amount of alcohol in such a relatively short time span will inevitably result in the tank pilot's complete inebriation, and, upon resuming his role behind the controls of his machine of death, he will likely be far too wasted to know the "fire giant canon" peddle from the break peddle. The theoretical outcome being either the drunken annihilation of his own team, or at least running several red lights and weaving in and out of traffic enough to get pulled over. The first case is obviously the better, but in the case of the latter, he will most definitely be at least issued a court date, until which he will have his license revoked and be unable to drive his tank, nullifying the threat. He also might die of severe hangover.